So-called stand-up screw guns, which are powered by means of trigger-actuated, electric motors, are exemplified in Murray U.S. Pat. No. 3,960,191, Dewey U.S. Pat. No. 4,236,555, and Dewey U.S. Pat. No. 4,397,412 and are available commercially from ITW-Buildex (a unit of Illinois Tool Works Inc.) of Itasca, Ill., under its AUTOTRAXX trademark.
Typically, stand-up screw guns employ driving members with driving tips, such as, for example, driving tips adapted to drive Phillips-head screws. Fastener-driving tools of other types, which may be powered by means of electric motors or by means of pneumatic motors, employ driving members with driving sockets, which fit axially over conforming heads of the fasteners, such as, for example, screws or bolts. Typically, the sockets and fastener heads are non-circular or polygonal when viewed axially. Commonly, the sockets and fastener heads are hexagonal when viewed axially.
Often, it is difficult for a user to center the non-circular socket of such a tool and the non-circular head of such a fastener, particularly if a stand-up screw gun is used. Although a bolt or machine screw can be manually started by means of rotating the same several turns into a prethreaded hole performed within a workpiece, it is difficult for a user to stabilize a screw having a non-circular head and having a drilling or tapping tip before the screw has been driven several turns into a workpiece. Centering of the non-circular socket of a fastener-driving tool and the non-circular head of such a screw can therefore be especially difficult for a user to achieve.
If the non-circular socket of such a fastener-driving tool and the non-circular head of such a fastener are not centered relative to each other, it is possible for the fastener, the workpiece, or both to be damaged if an attempt is made to drive the fastener into the workpiece by means of the fastener-driving tool. The non-circular socket may also be damaged.
Therefore, there has been a need, to which this invention is addressed, for an improved mechanism to center the non-circular socket of such a fastener-driving tool and the non-circular head of such a fastener relative to each other.